SCIENTIFIC TRANSACTIONS 
OF THE 
BOQ Wel ID WIBIGIIN SOMA ye, 
VOLUME VII. 
If, 
A DETERMINATION OF THE WAVE-LENGTHS OF THE PRINCIPAL LINES 
IN THE SPECTRUM OF GALLIUM, SHOWING THEIR IDENTITY WITH 
TWO LINES IN THE SOLAR SPECTRUM. By W. N. HARTLEY, F.BS., 
anp HUGH RAMAGEH, A.R.C.Sc.1. 
(Puate I.) 
[Read Marca 16, 1898. | 
Ir haying been shown by us* in the examination of a number of minerals, such as 
felspar, mica, basalt, pumice from Krakatoa, volcanic dust from New Zealand, 
iron ores, aluminous minerals, and of meteoric iron and meteoric dust, that 
gallium is a common constituent, present only in small proportion, it seemed of 
interest to determine whether traces of this element are to be found in the solar 
spectrum. 
In order to test this matter by a more accurate investigation than is possible 
with ordinary instruments, we have been glad to avail ourselves of the very kind 
offer of assistance made by Dr. W. E. Adeney, Curator of the Royal University 
of Ireland. He has afforded us the means of photographing spectra with the fine 
Rowland concave grating of twenty-one and a-half feet radius which has been 
mounted in the Physical Laboratory of the University. The instrument was 
adjusted so that we could photograph on one plate, 194 inches long, the region, 
in the second order, between wavye-lengths 3990 and 4500. Cadet ‘ Lightning 
plates” were used, and they were developed with hydroquinone. 
* Proc. Royal Society, vol. 60, pp. 85 and 893. Trans. Chemical Society, 1897, pp. 5383 and 547. 
Journal Iron and Steel Institute, 1897, No.ii., p. 182. Scientific Proc. Roy. Dub. Soc., vol. viii. (N.S.), 
Part vi., No. 68. 
TRANS. ROY, DUB. SOC., N.S. VOL. VII., PART I. B 
